Facebook banned an ad last week featuring plus-size model Tess Holliday wearing a bikini, telling an Australian feminist group that their image violates the platform's Health and Fitness Policy.

Cherchez La Femme (CLF) is a Melbourne-based organization that hosts a monthly talk show on current affairs with "an unapologetically feminist angle." Their ad featuring Holliday promotes an upcoming event, Cherchez La Femme: Feminism and Fat, a show to discuss fat acceptance in today's society.

But Facebook refused to promote it, telling CLF that the image violated its policy of not promoting "close-ups of 'muffin tops,'" tight clothes and "medical conditions [shown] in a negative light," such as eating disorders, because it "depicts a body or body parts in an undesirable manner."

"Ads may not depict a state of health or body weight as being perfect or extremely undesirable," Facebook's Ads team explains in their message. "Ads like these are not allowed since they make viewers feel bad about themselves. Instead, we recommend using an image of a relevant activity, such as running or riding a bike."

But CLF and its supporters are using Facebook's reaction as proof that complete acceptance still has a long way to go.

"Facebook has ignored the fact that our event is going to be discussing body positivity (which comes in all shapes and sizes, but in the particular case of our event, fat bodies), and has instead come to the conclusion that we've set out to make women feel bad about themselves by posting an image of a wonderful plus sized woman," CLF producer Jess Gleeson writes in a post on the group's Facebook page.

"Facebook seemingly has no idea that plus sized, self-describing fat women can feel great about themselves," adds Gleeson. And ironically, CLF's ad featuring Holliday promotes an event to counter this exact idea.

Holliday (previously known as Tess Munster) made history in January when she became the largest plus-size model to sign with a major modeling agency. Contracted plus size models at major agency are typically taller than 5'8" and between a size 8 and 16. Holliday, however is 5'5" and a size 22.

Facebook has since apologized for their response to CLF, calling it a mistake.

But for people embracing health and happiness in a variety of body shapes and sizes, such "mistakes" can send a discouraging message.

"We put women in a terrible bind," Northwestern University professor Renee Engeln, an expert on "objectification theory," body image and the media, told The Monitor's Lisa Suhay last year. "So often, they hear that what matters most is their beauty. But then we provide such a narrow definition of beauty that they always feel they're falling short of the standard. If models like Tess can help to expand the definition of beauty, that's a positive step."

Sports Illustrated's Swimsuit Issue in February featured Ashley Graham – the first plus-sized model to grace the magazine's cover.

But even though Graham is now an SI cover girl, she still experiences similar discriminatory situations. Graham was featured in an ad for Lane Bryant's new lingerie line for plus-sized women in March, but ABC and NBC both banned the ad, citing the networks' indecency guidelines. Lane Bryant and its supporters don't believe this explanation, arguing that the networks feature equally racy ads by Victoria's Secret and others.

"I don't think these models are any more nude than any other models we've seen on TV," a rep for Lane Bryant told the New York Daily News in March. Networks also turned down a similar ad from the company in 2010.

"Victoria's Secret commercials are airing all throughout the day, but when it comes to a Lane Bryant commercial, we have a little bit of extra, you know, overflowing, and then everybody freaks out," Graham told CBS News in 2010.

And it's not just ads: plus-size American women say they have a hard time seeing themselves in retail stores.

Despite being a $17 billion dollar industry, the plus-size market is still growing at a pace below what many retailers want to see before they invest more. Currently, the market is expanding at about two percent, but that may have to speed up to four or five percent before fashion really starts paying attention, as NPR reported.

Many plus size women feel that fewer styles are sold for their clothing size. But the market recently welcomed two additions who promise to shake up plus size offerings: actresses Melissa McCarthy and Rebel Wilson have designed their own clothing brands to help fill the gap.